1. Field of the Invention
The present invention relates to the field of gas turbine engines and jet propulsion. More particularly, the present invention relates to a combustor and gas compressor for use in a gas turbine engine.
2. Description of the Prior Art
Several past devices have been used to increase the pressure of a gas. These devices include, but are not limited to, gas turbines, constant volume combustors, pulse jets, thermal pulse combustors, pulse detonation jets, reciprocating compressors, axial compressors and centrifugal compressors.
Many of these prior devices, including constant volume combustors, pulse jets, thermal pulse combustors, and pulse detonation jets have used the force of combustion to increase gas pressure or induce gas flow. In each of these devices, a single output stream is utilized to discharge gasses from a combustion chamber. The output stream often contains combustion products diluted with excess unconsumed air, depending upon the operating temperature of the device. As a result of the combustion cycle, the output stream is generally high in temperature and intermittent in nature.
The intermittent nature and high temperature of the output stream makes the output from the prior art devices unsuitable for many compressed air applications. For example, the output temperature may be too high for use in a turbine or the intermittent nature of the output may cause stress and surging in the turbine. Any attempt to decrease the exhaust temperature by burning a lean combustible mixture results in poor combustion characteristics and generation of undesirable emissions. Further, when the prior art devices are used as jet engines, they are limited by the need to operate at high temperatures to gain thermal efficiency. This high temperature limits the amount of air handled, and this in turn limits the mass flow, an important element in determining the efficiency of a jet engine, because most or all of the air entering the device is consumed and discharged as combustion products.
If the excess unconsumed air could be separated from the spent gasses in the output stream and recovered as a pressurized, cooler stream, the unconsumed air could be used for a variety of applications. In one such application, the pressurized unconsumed product is used to compress air within the combustion chamber during a compression step of the operating cycle, thereby further increasing the pressurized output from each compression step. By this application, the mass of air handled per unit of energy delivered would be increased, and the specific output of the engine would also be increased. In other applications, the pressurized unconsumed product may be delivered through a nozzle for use as ajet engine, distributed to a turbine to provide rotational power, or used as a simple air compressor. Such a cycle would result in a large fraction of the air handled being transformed to compressed, unconsumed air at slightly elevated temperatures and the fraction of air remaining being exhausted at ambient pressure and elevated temperature.
Other of the prior art devices, including reciprocating compressors, axial compressors, and centrifugal compressors, are limited by their requirement of an external power source to provide the energy for compression of the air. If an internal power source could be used to provide energy for air compression, the compressor could be simplified.
Accordingly, it is an advantage of the present invention to provide an air compressor having separate pressurized air product and exhaust streams, such that the pressurized air product stream may be used separately from the exhaust stream.
It is another advantage of the invention to provide an air compressor wherein the pressurized air product output stream is held in a receiving tank and then used to further compress gasses in a combustion chamber before combustion of the gasses.
A further advantage of the invention is to provide a simplified air compressor which does not require a large external power source for operation.
It is a further advantage of the proposed device to offer simpler construction and operation than gas turbines and reciprocating, axial, and centrifugal compressors, and greater ranges of operation than pulse combustion devices such as detonation engines, pulse combustors, and pulse jets.